The present invention generally relates to guide structures for guiding endless magnetic tapes, and more particularly to a guide structure for guiding an endless magnetic tape in an endless video tape recorder which plays the endless magnetic tape.
In audio tape recorders, there is an audio tape recorder which uses a tape cartridge which accommodates an endless magnetic tape having the shape of an endless loop. By using this tape cartridge in place of the existing video tape cassette having two reels, it is in principle possible to realize an endless video tape recorder which can record and/or reproduce information in an endless manner.
However, there are strict requirements on video tape recorders, and it is required that a load acting on the tape transport is small and the tape transport is stable. Especially in a video tape recorder which plays an endless magnetic tape which is wound on a stationary reel in the form of a tape roll and the tape is drawn out to the inside of the stationary reel from an innermost turn of the tape roll, the load acting on the tape transport is large due to friction between the tape and the stationary reel. Hence, measures must be taken to reduce the load acting on the tape transport.
In the video tape recorder which uses the stationary reel, the tape which is drawn out to the inside of the stationary reel from the innermost turn of the tape roll must pass over or under the stationary reel in order to reach an outermost turn of the tape roll to be taken up on the tape roll. It is unavoidable that the height of the tape path greatly changes. When the height of the tape path changes, the tape transport easily becomes unstable and the tape is easily damaged. For this reason, the tape path must be selected so as to minimize the instability of the tape transport and minimize the damage to the tape. In addition, the tape is inevitably twisted when the tape is drawn to from the innermost turn of the tape roll and then returned to the outermost turn of the tape roll. Therefore, this kind of endless video tape recorder is impractical in that the tape transport is unstable at a part where the information recording and/or reproduction is carried out and the tape is easily damaged because the tape is drawn out from the innermost turn of the tape roll while being twisted.
FIG. 1 shows an essential part of an example of the conventional endless video tape recorder. In FIG. 1, the essential part of the endless video tape recorder has a stationary reel 1 which cannot rotate, a stationary head 2, a capstan 3, a pinch roller 4, an overturn guide 5, a head moving mechanism 6, an endless magnetic tape 7 which has the shape of an endless loop, and a tape roll 8 made up of the tape 7 which is woun on the stationary reel 1.
When the capstan 3 is rotated in a direction A and the tape 7 is driven in a state pinched between the capstan 3 and the pinch roller 4, the tape 7 at an innermost turn of the tape roll 8 is drawn out to the inside of the stationary reel 1. The drawn out tape 7 makes sliding contact with the stationary head 2 and is then guided by the overturn guide 5. The transport direction of the tape 7 is changed by the overturn guide 5 and the tape 7 reaches an outermost turn of the tape roll 8 to be taken up on the stationary reel 1. The tape 7 is thus transported in a forward direction A.sub.1 when the capstan 3 rotates in the direction A.
The stationary head 2 is shifted in the width direction of the tape 7 by the head moving mechanism 6 every time the tape 7 makes one round. Hence, a video track 9 shown in FIG. 2 is formed on the tape 7. When the stationary head 2 is shifted to a final position, the head moving mechanism 6 then shifts the stationary head 2 back to the original position. In FIG. 2, a start position 10 of the track 9 corresponds to the original position of the stationary head 2 and an end position 11 of the track 9 corresponds to the final position of the stationary head 2.
In the tape path from a position after the tape 7 passes the stationary head 2 to the outermost turn of the tape roll 8, the tape 7 is transported while being twisted. Therefore, there are problems in that the tape transport becomes unstable and the tape 7 is easily damaged due to the twist.
Furthermore, since the stationary head 2 is used for the information recording and/or reproduction, the tape 7 is transported at a high speed v.sub.1 of 5.5 m/sec. Because of the high tape transport speed v.sub.1, there are problems in that the tape 7 is easily damaged, the load acting on the tape transport is large, the tape 7 is heated, the tape transport is unstable, the reliability of the endless video tape recorder becomes poor and the like
On the other hand, the start position 10 and the end position 11 of the video track 9 are discontinuous. From this point of view, the recording and/or reproduction cannot be carried out continuously even though the tape 7 has the shape of an endless loop.